This procedure began as the first stage of a bariatric surgery called biliopancreatic diversion. This surgery had two stages. The sleeve gastrectomy reduced the patient's surgical risks for the second stage of the surgery by promoting significant weight loss. Because many patients were very successful with weight loss after undergoing sleeve gastrectomy, they decided with their surgeons to not have the second stage of the surgery.
A sleeve gastrectomy creates a small "sleeve" of a stomach that looks like a tube or a banana. This surgery removes about 80% of the stomach. As you would expect, patients lose weight by limiting how much food they can take in. It is also thought to contribute to weight loss by removing the part of the stomach that make grehlin, a hormone responsible for appetite.
Most patients will lose 50% of their excess body weight in the first year. No data is yet available for five-year outcomes. Therefore, doctors still consider this an experimental procedure since they do not really know how the surgery works for long-term weight loss and maintenance. However, available studies show that weight loss remains stable after the first year.